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THE 



TREATMENT OF STEEL. 



A SERIES OF CIRCULARS 



ON 



Heating, Annealing, Forging andTempering, 



; 






ISSUED BY THE 



f CRESCENT STEEL WORKS. 

I 

,J.%i.i.h 

PITTSBURGH : 
MILLER, METCALF & PARKIN. 

1881. 










Copyright, 1881, 
By MILLER, METCALF & PARKIN. 



i KKIGHT & LEONARD . 1 



^ijOiu 



PREFACE. 



FROM time to time our friends ask of us questions con- 
cerning steel, its correct treatment and management, and 
we have therefore thought it proper to combine in one form 
circulars issued by us in previous years. At the same time 
we add some new and, we hope, interesting matter. 

We trust that it may be accepted as an effort on our 
part to assist in overcoming difficulties connected with the 
working of steel. 

Many will find in it nothing new; others may be able 

to select something of interest and profit. 

M. M. & P. 
Pittsburgh, July i, 1881. 



THE TREATMENT OF STEEL. 



AN English steel manufact- 
urer remarks: "We do not 
analyze for carbon because 
we find by long experience 
that the eye can judge of the 
percentage of carbon in an 
ingot of cast steel of the 
highest tempers from the ap- 
pearance of the fracture more 
accurately than the chemist 
can ascertain by any method 
of analysis hitherto discov- 
ered." 

We do not indorse this as 
a whole, but to show the re- 
liability of " inspection by the eye " we give the result of tests 
made in 1874 and 1875. 

In April, 1874, we selected eight ingots, by our numbers, 
from the ingots as they were piled up for use. The figures 
in the second column show the amounts of carbon in these 
eight ingots as determined by analysis. 

In March, 1875, twelve ingots were selected in the same 
way, one being below the series of eight and the others being 
within the limits of the eight, Nos. 5, 7 and 10 being inter- 
polations. 

It will be seen that the carbon runs up with the numbers 

7 




8 



THE TREATMENT OF STEEL. 



without a break, thus proving by careful analysis that our 
methods were careful and reliable. 

The mean difference in carbon is only seven-hundredths 
of one per cent. As there is no possibility of a skillful and 
careful person mistaking any one of these numbers for 
another, our patrons can judge for themselves of the proba- 
bility of receiving steel of uniform temper and properly 
adapted to the work to be done. 

The structure of the ingot is invariably the same for the 
same amount of carbon, and the observance of this rule is 
the steel maker's guide and the steel user's safety. 

Analyses made by Prof. John W. Langley, University of 
Michigan, Ann Arbor, Michigan : 



No. 



I 

2 

3 

4 

5 

6 

7 ■■ 

8 

9 

io 

ii 

12 

Mean differences 



Carbon. 



March, 1875, 



.302 
.490 

•529 
.649 

.So i 

.S41 

.S67 

.87 1 

•955 
1.005 
1.05S 
1.079 



.071 



Carbon. 



April, 1874. 



.404 

•599 
•7S9 

'.856 

.867 
•939 

1036 
1. 116 



.102 



Carbon. 


Differ- 
ences. 


Mean of the 
two preced- 
ing columns. 


.302 

•447 
•564 
.719 
.So 1 
.S 4 S 
.S67 
.S69 

•947 
1.005 
1.047 
1.097 


•1*45 
.117 

•155 
.0S2 

.047 
.019 
.002 
.07S 
•0 5 S 
.042 
.050 





.072 



Iron by 
Differ- 
ence. 



99.614 

99-454 
99363 
99.270 
99.119 
99.0S5 
99.044 
99.040 
9S.900 
9S.860 
9S.752 

93-753 



The figures in this table are tractions of one per cent. 



ON ANNEALING, 



|VVING to the fact that the opera- 
tions of rolling or hammering 
steel make it very hard, it is 
frequently necessary that the 
steel should be annealed before 
it can be conveniently cut into 
required shapes for tools. 

Annealing or softening is ac- 
complished by heating steel to 
a red heat and then cooling it 
very slowly, to prevent it from 
getting hard again. 

The higher the degree of 
heat, the more the steel will be 
softened, until the limit of soft- 
ness is reached when the steel is melted. 

It does not follow that the higher a piece of steel is 
heated, the softer it will be when cooled, no matter how 
slowly it may be cooled ; this is proved by the fact that an 
ingot is always harder than a rolled or hammered bar made 
from it. 

Therefore, there is nothing gained by heating a piece of 
steel hotter than a good bright cherry red ; on the contrary, 
a higher heat has several disadvantages : 

First — If carried too far, it may leave the steel actually 
harder than a good red heat would leave it. 




IO THE TREATMENT OF STEEL. 

Second — If a scale is raised on the steel, this scale will 
be harsh, granular oxide of iron, and will spoil the tools used 
to cut it. It often occurs that steel is scaled in this way, 
and then because it does not cut well, it is customary to 
heat it again, and hotter still, to overcome the trouble ; while 
the fact is, that the more this operation is repeated, the 
harder the steel will work, because of the hard scale and the 
harsh grain underneath. 

Third — A high scaling heat, continued for a little time, 
changes the structure of the steel, destroys its crystalline 
property, makes it brittle, liable to crack in hardening, and 
impossible to refine. 

Again, it is a common practice to put steel into a hot fur- 
nace at the close of a day's work, and leave it there all 
night. This method always gets the steel too hot, always 
raises a scale on it, and worse than either, it leaves it soak- 
ing in the fire too long; and this is more injurious to steel 
than any other operation to which it can be subjected. 

A good illustration of the destruction of crystalline struct- 
ure by long continued heating may be had by operating on 
chilled cast iron. 

If a chill be heated red hot and removed from the fire as 
soon as it is hot, it will, when cold, retain its peculiar crys- 
talline structure ; if now it be heated red hot, and left at a 
moderate red for several hours ; in short, if it be treated as 
steel often is, and be left in a furnace over night, it will be 
found, when cold, to have a perfect amorphous structure, 
every trace of chill crystals will be gone, and the whole piece 
will be non-crystalline gray cast iron. If this is the effect 
upon coarse cast iron, what better is to be expected from 
fine cast steel ? 



ON ANNEALING. II 



A piece of fine tap steel after having been in a furnace 
over night will act as follows : 

It will be harsh in the lathe and spoil the cutting tools. 

When hardened it will almost certainly crack; if it does 
not crack it will have been a remarkably good steel to begin 
with. When the temper is drawn to the proper color and 
the tap is put into use, the teeth will either crumble off or 
crush down like so much lead. 

Upon breaking the tap the grain will be coarse and the 
steel brittle. 

To anneal any piece of steel, heat it red hot ; heat it uni- 
formly and heat it through, taking care not to let the ends 
and corners get too hot. 

As soon as it is hot take it out of the fire, the sooner the 
better, and cool it as slowly as possible. A good rule for 
heating is to heat it at so low a red that when the piece is 
cold it will still show the blue gloss of the oxide that was put 
there by the hammer or the rolls. 

Steel annealed in this way will cut very soft; it will 
harden very hard, without cracking, and when tempered it 
will be very strong, nicely refined and will hold a keen, 
strong edge. 



ON HEATING STEEL. 




WING to varying instructions 
on a great many different labels, 
we find at times a good deal of 
misapprehension as to the best 
way to heat steel ; in some cases 
this causes too much work for 
the smith, and in other instances 
disasters follow the act of hard- 
ening. 

There are three distinct 
stages, or times of heating : 
First, for forging. 
Second, for hardening. 
Third, for tempering. 
The first requisite for a 
good heat for forging is a 
clean fire and plenty of fuel, 
so that jets of hot air will 
not strike the corners of the 
piece ; next, the fire should be regular, and give a good 
uniform heat to the whole part to be forged. It should be 
keen enough to heat the piece as rapidly as may be, and 
allow it to be thoroughly heated through, without being so 
fierce as to overheat the corners. 

The trouble in the forge fire is usually uneven heat, and 
not too high heat. Suppose the piece to be forged has been 



ON HEATING STEEL. 1 3 

put into a very hot fire, and forced as quickly as possible to 
a high yellow heat, so that it is almost up to the scintillating 
point. If this be done, in a few minutes the outside will be 
quite soft and in nice condition for forging, while the mid- 
dle parts will be not more than red hot. The highly heated 
soft outside will have very little tenacity ; that is to say, this 
part will be so far advanced toward fusion that the particles 
will slide easily over one another, while the less highly 
heated inside parts will be hard, possessed of high tenacity, 
and the particles will not slide so easily over each other. 

Now let the piece be placed under the hammer and 
forged, and the result will be as shown in Fig. i. 




Fig. i. Fig. 2. 

The soft outside will yield so much more readily than the 
hard inside, that the outer particles will be torn asunder, 
while the inside will remain sound, and the piece will be 
pitched out and branded "burned." 

Suppose the case to be reversed and the inside to be 
much hotter than the outside ; that is, that the inside shall 
be in a state of semi-fusion, while the outside is hard and 
firm. 

Now let the piece be forged and we shall have the case 
as shown in Fig. 2. The outside will be all sound and the 
whole piece will appear perfectly good until it is cropped, 
and then it is found to be hollow inside, and it is pitched 
out and branded "burst." 

In either case, if the piece had been heated soft all 



14 THE TREATMENT OF STEEL. 

through, or if it had been only red hot all through, it could 
have been forged perfectly sound and good. 

If it be asked, why then is there ever any necessity for 
smiths to use a low heat in forging, when a uniform high 
heat will do as well, we answer : 

In some cases a high heat is more desirable to save heavy 
labor, but in every case where a fine steel is to be used for 
cutting purposes, it must be borne in mind that very heavy 
forging refines the bars as they slowly cool; and if the smith 
heats such refined bars until they are soft, he raises the 
grain, makes them coarse, and he cannot get them fine again 
unless he has a very heavy steam hammer at command and 
knows how to use it well. 

In following the above hints there is a still greater danger 
to be avoided : that is incurred by letting the steel lie in the 
fire after it is properly heated. When the steel is hot 
through it should be taken from the fire immediately and 
forged as quickly as possible. 

" Soaking " in the fire causes steel to become " dry " and 
brittle, and does it more injury than any bad practice known 
to the most experienced. 

By observing these precautions a piece of steel may al- 
ways be heated safely, up to even a bright yellow heat, when 
there is much forging to be done on it ; and at this heat it 
will weld well. 

The best and most economical of welding fluxes is clean, 
crude borax, which should be first thoroughly melted and 
then ground to fine powder. Borax prepared in this way 
will not froth on the steel, and one half of the usual quantity 
will do the work as well as the whole quantity unmelted. 

After the steel is properly heated it should be forged to 
shape as quickly as possible, and just as the red heat is leav- 



ON HEATING STEEL. 1 5 

ing the parts intended for cutting edges, these parts should 
be refined by rapid light blows, continued until the red dis- 
appears. 

For the second stage of heating for hardening great care 
should be used, first, to protect the cutting edges and work- 
ing parts from heating more rapidly than the body of the 
piece; next, that the whole part to be hardened be heated 
uniformly through, without any part becoming visibly hotter 
than the other. A uniform heat, as low as will give the 
required hardness, is the best for hardening. 

BEAR IN MIND, that for every variation of heat 
which is great enough to be seen there will result a varia- 
tion in grain, which may be seen by breaking the piece, 
and for every such variation in temperature there is a very 
good chance for a crack to be seen. Many a costly tool is 
ruined by inattention to this point. 

The effect of too high heat is to open the grain, to 
make the steel coarse. 

The effect of an irregular heat is to cause irregular 
grain, irregular strains, and cracks. 

As soon as the piece is properly heated for hardening it 
should be promptly and thoroughly quenched in plenty of 
the cooling medium, water, brine or oil, as the case may be. 

An abundance of the cooling bath, to do the work quickly 
and uniformly all over, is very necessary to good and safe 
work. 

To harden a large piece safely a running stream should 
be used. 

Much uneven hardening is caused by the use of too small 
baths. 

For the third stage of heating; to temper, the first impor- 
tant requisite is again uniformity. The next is time; the 



i6 



THE TREATMENT OF STEEL. 



more slowly a piece is brought down to its temper, the better 
and safer is the operation. 

When expensive tools, such as taps, rose cutters, etc., are 
to be made, it is a wise precaution, and one easily taken, to 
try small pieces of the steel at different temperatures, so as 
to find out how low a heat will give the necessary hardness. 
The lowest heat is the best for any steel, the test costs noth- 
ing, takes very little time, and very often saves considerable 
losses. 




FURNACES. 




|E present in this connection sketches 
^Jl of a cheap and handy furnace for 
[J use in a blacksmith shop, adapted 
jl especially for heating steel, and more 
[J particularly for heating steel for hard- 
ening. 

The furnace is so simple that the 
sketches need no explanation; for 
binders, ten pieces of old rail about six feet long with one 
end set in the ground and the tops tied by ^ inch rods are 
all that is necessary, with a piece of iron about 3x5^ inches 
running around near the top, and set in flush with the bricks. 
The distinctive features of this furnace are the fire bed 
and a good damper on the stack. In an experience of many 
years we have found nothing better than the Tupper grate- 
bar with half-inch openings. These bars set in as shown 
make a level, permanent bed, and give an evenly distributed 
supply of air to the fuel. In such a furnace as this one set 
of bars will last for years and remain level. 

While on the subject of grate-bars we may as well say 
that the satisfactory and safe working of this furnace would 
be entirely defeated by any attempt to use either square 
wrought-iron bars or ordinary straight cast-iron bars. Such 
bars always warp, get pushed out of place, and allow a rush 
of air through at one place and no air at another. This 
causes hot and cold places in the furnace and produces 

17 



i8 



THE TREATMENT OF STEEL. 



uneven heating, which is the chief source of cracking in 
hardening, and also the air rushing through the large holes 
will burn the steel. A bar must be used which will remain 
level and in its place, and the smaller and more numerous 
the openings are the better will be the result. 

Clean hard coke is the only proper fuel for such a furnace 
and for such work. The furnace should be filled full up to 
the fore plate, or better, a little higher, — with coke in pieces 

SEC Tl OH OF STACK 



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13'™ SG > 



(4/ IN) 



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CO 
CO 



no larger than an ordinary man's fist, — but the smaller the 
better. 

When it is used for heating for forging purposes the 
damper may be left high enough to run the furnace as hot 
as may be required, — if necessary, a welding heat can be 
obtained. 

When used for hardening the furnace should be got as 
hot as is needed before the steel is put into it, then when the 
steel is put in the damper should be dropped down tight. 

The door, which is 12 inches high and 24 inches wide, 
should be nicely balanced by a lever and weight, with a rod 



FURNACES. 



J 9 



in a handy place so that the operator can pull it up easily 
and turn over his pieces from time to time, so as to get his 
heat perfectly uniform. 

In the clear gas of a coke fire the whole interior of a fur- 
nace can be seen easily, and every piece can be watched as 



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it ought to be. Time, care, watchfulness and absolute uni- 
formity of heat are the essentials necessary for success in 
hardening steel. 

Every large shop should have such a furnace, and should 
have one man trained to its use, to do the hardening and 
tempering for the whole shop. Such a furnace in the hands 
of a careful man in any railroad shop in the country would 
pay for itself every year and save the man's wages besides. 



20 



THE TREATMENT OF STEEL. 



The furnace will consume very little coke at any time, 
and when not in use, with the damper down it will stay hot 
a long time and waste the coke but a trifle. 

There is no more absurd nor wasteful system than that of 
requiring a smith at his anvil to harden and temper his work. 
His fire is not fit to heat in, to begin with, and he never has 
time to do his work properly if it were. 

From such a furnace as is here described we harden all 



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£5 



SECTION AT CD 



B 



sorts of tools, taps, small dies, large rolls, rotary shear knives, 
and shear knives as large as five feet long, which is the whole 
length of the furnace. 

The steel which is tempered best is that which is the 
finest in the grain and the strongest. The best way to test 
both grain and strength is to hammer out a piece to about 
1 X A x H inch, a foot or so in length, and temper to a high 
blue, or pigeon-wing, and when cold to break it off in little 
pieces with a hand hammer. 



FURNACES. 2 1 



A little practice will soon enable a man to determine, first, 
whether he heated his piece to just the right point. The file 
and the appearance of the grain will determine this point. 
Next, when a little experience as to heat has been gained, 
he will know by the strength and grain whether his steel is 
really good, or whether it is "dry" and poor. 

In every shop there are plenty of worn-out tools of all 
sorts in the scrap-heap ; the temperer should be allowed to 
spend all of his leisure time in hammering these out and 
testing them as above. The steel will cost nothing, and the 
knowledge gained will pay for the time over and over again. 
We say to our friends again that if you will heat even the 
finest steel in dirty slack fires you will get dirty coats of sul- 
phurous oxides on it, and no good results. 



EFFECTS OF HEAT UPON STEEL. 



WE now present an illustration 
of the effect of heat upon steel, 
which is a direct reproduction 
upon paper of the grain of the 
steel by means of the heliotype 
process. 

Description. — Take a bar 
of steel of ordinary size, say 
about an inch by a half, and 
heat six or eight inches of one 
end to a low red heat, and nick 
the heated part all around the 
bar at intervals of half to three- 
quarters of an inch, until eight 
or nine. notches are cut. This nicking is done at red heat, 
to determine the fractures at the nicks. Next place the 
end of the bar in a very hot fire and heat it white hot until 
it scintillates at the extreme end, leaving the other parts 
enough out of the fire to heat them only by conduction. Let 
the end remain in the fire until the last piece nicked is not 
quite red red-hot, and the next to the last barely red hot. 

Now, if the pieces be numbered from one to eight, com- 
mencing at the outer end, No. i will be white or scintillating 
hot, No. 2 will be white hot, No. 3 will be high yellow hot, 
No. 4 will be yellow or orange hot, No. 5 will be high red 





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future date. 



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EFFECTS OF HEAT UPON STEEL. 27, 



hot, No. 6 will be red hot, No. 7 will be low red hot, No. 8 
will be black hot. 

As soon as heated, let the bar be quenched in cold water 
and kept there until quite cold. After cooling, the bar 
should be carefully wiped dry, especially in the notches. An 
examination by the file will reveal the following, if high steel 
has been used : 

No. 1 will scratch glass, Nos. 2, 3 and 4 excessively hard, 
Nos. 5 and 6 well hardened, No. 7 about hard enough for tap 
steel, No. 8 not hardened. 

In breaking off the pieces over the corner of the anvil 
they should be caught in a clean keg or box, to keep the 
fractures clean and bright. 

No. 1 will be as brittle as glass, No. 2 will be nearly as 
brittle as glass, Nos. 3, 4 and 5 will break off easily, each a 
little stronger than the other, Nos. 6 and 7 will be very 
strong, and much stronger than No. 8, or the bar unhardened. 

Place the pieces in the order of their numbers fitting the 
fractures, then upend each one, beginning with No. 1 and 
following with each in the order in which they lie, and the 
result will be fractures as shown so beautifully in our illus- 
tration, each differing from the other. 

No. 1 will be coarse, yellowish cast, and very lustrous; 
No. 2 will be coarse and not quite so yellow as No. 1 ; No. 3 
will be finer than 1 or 2, and coarser than No. 8, and will 
have fiery luster; No. 4, like No. 3, not quite so coarse, yet 
coarser than No. 8; No. 5 will be about the same size grain 
as No. 8, but will have fiery luster; No. 6 will be much finer 
than No. 8, will have no fiery luster, will be hard through 
and very strong. This is what is called refining by hard- 
ening. No. 7 will be refined and hard on the corners and 
edges, and rather coarser, and not quite so hard in the 



24 THE TREATMENT OF STEEL. 

middle. This is about the right heat for hardening taps, 
milling tools, etc., the teeth of which will be amply hard, 
while there will be no danger of cracking the tool. No. 8 
illustrates the original grain of the bar. 

In nine cases out of ten the bar will crack along the 
middle to the refined piece. In the illustration the crack 
shows very plainly in No. 4, but we have never known this 
crack to extend into the refined piece, although we have 
repeated the experiment many times. We learn from this 
experiment the following: 

First, "0" Any difference in temperature sufficiently great 
to be seen by the color will cause a corresponding difference 
in the grain, "b" This variation in grain will produce inter- 
nal strains and cracks. 

Second, Any temperature so high as to open the grain so 
that the hardened piece will be coarser than the original bar 
will cause the hardened piece to be brittle, liable to crack, 
and to crumble on the edges in use. 

Third, A temperature high enough to cause a piece to 
harden through, but not high enough to open the grain, will 
cause the piece to refine, to be stronger than the untem- 
pered bar, and to carry a tough, keen, cutting edge. 

Fourth, A temperature which will harden and refine the 
corners and edges of a bar, but which will not harden the 
bar through, is just the right heat at which to harden taps, 
rose-bitts and complicated cutters of any shape, as it will 
harden the teeth sufficiently without risk of cracking, and 
will leave the mass of the tool soft and tough, so that it can 
yield a little to pressure and prevent the teeth tearing out. 
These four rules are general, and apply equally well to any 
quality of steel or to any temper of steel. 

Steel which is so mild that it will not harden in the ordi- 



EFFECTS OF HEAT UPON STEEL. 25 

nary acceptance of the term will show differences of grain 
corresponding to variations in temperature. 

To restore any of the first seven pieces shown to the 
original structure as shown in No. 8, it is only necessary to 
heat it through to a good red heat, not to a high red, allow it 
to stay at this temperature for ten minutes to thirty minutes, 
according to the size of the piece, and then to cool slowly. 
If upon the first trial the restoration should be found incom- 
plete, and the piece upon being fractured should still show 
some fiery grains, a second heating continued a little longer 
than the first would cause a restoration of fracture. This 
property of restoration is not peculiar to any steel, and its 
performance requires no mysterious agencies beyond those 
given above. 

It should be distinctly borne in mind that a piece restored 
from overheating is never quite as good as it would have re- 
mained if it had never been abused, and we strongly advise 
that no occasion should ever be given for the use of this 
process of restoration except as an interesting experiment. 
The original and proper strength of fine steel can never be 
fully restored after it has once been destroyed by over- 
heating. 



ON TEMPER OF STEEL. 




[HE word temper, as used by 
the steel maker, indicates the 
amount of carbon in steel ; 
| thus, steel of high temper is 
steel containing much carbon ; 
steel of low temper is steel 
containing little carbon ; steel 
of medium temper is steel con- 
taining carbon between these 
limits, etc. Each number of 
our carbon circular represents 
a temper, and besides these 
numbers we use intermediate 
ones, amounting to some twenty 
in all. As the temper of steel 
can only be observed in the 
ingot, it is not necessary to the needs of the trade to attempt 
any description of the mode of observation, especially as this 
is purely a matter of education of the eye, only to be obtained 
by years of experience. 

The act of tempering steel is the act of giving to a piece 
of steel, after it has been shaped, the hardness necessary for 
the work it has to do. This is done by first hardening the 
piece, generally a good deal harder than is necessary, and 
then toughening it by slow heating and gradual softening 

until it is just right for work. 

26 



ON TEMPER OF STEEL. 2J 

A piece of steel properly tempered should always be finer 
in grain than the bar from which it was made. If it is neces- 
sary, in order to make the piece as hard as is required, to 
heat it so hot that after being hardened it will be as coarse 
or coarser in grain than the bar, then the steel itself is of too 
low temper for the desired work. In a case of this kind, the 
steel maker should at once be notified of the fact, who should 
immediately correct the trouble by furnishing higher steel. 

If a great degree of hardness is not desired, as in the case 
of taps, and most tools of complicated form, and it is found 
that at a moderate heat the tools are too hard and are liable 
to crack, the smith should first use a lower heat in order to 
save the tools already made, and then notify the steel maker 
that his steel was too high, so as to prevent a recurrence of 
the trouble. In all cases where steel is used in large quan- 
tities for the same purpose, as in the making of axes, springs, 
forks, etc., there is very little difficulty about temper, be- 
cause, after one or two trials, the steel maker learns what his 
customer requires, and can always furnish it to him. 

In large, general works, however, such as rolling-mill and 
nail factory, or large machine works, or large railroad shops, 
both the maker and worker of the steel labor under great 
disadvantages from want of a mutual understanding. 

The steel maker receives his order and fills the sizes of 
tempers best adapted to general work, and the smith usually 
tries to harden all tools at about the same heat. The steel 
maker is right, because he is afraid to make the steel too 
high or too low, for fear it will not suit, and so he gives an 
average adapted to the size of the bar. 

The smith is right, because he is generally the most hur- 
ried and crowded man about the establishment. He must 
forge a tap for this man, a cold nail knife for that one, and a 



28 THE TREATMENT OF STEEL. 

lathe cutter for another, and so on ; and each man is in a 
hurry. 

Under these circumstances he cannot be expected to stop 
and test every piece of steel he uses, and find out exactly at 
what heat it will harden best, and refine properly. 

He needs steel that will all harden properly at the same 
heat, and this he usually gets from the general practice 
among steel makers, of making each bar of a certain temper, 
according to its size. 

But if it should happen that he were caught with only one 
bar of say inch and a quarter octagon, and three men should 
come in a hurry, one for a tap, another for a punch, and an- 
other for a chilled roll plug, he would find it very difficult to 
make one bar of steel answer for all of these purposes, even 
if it were of the very best quality, and the chances are that 
he would make one good tool and two bad tools. 

There is a perfectly easy and simple way to avoid all of 
this trouble ; and that is, to write after each size the pur- 
pose for which it is wanted, as for instance : Track tools, 
smith tools, lathe tools, taps, dies, cold nail knives, cold nail 
dies, hot nails, hot or cold punches, shear knives, etc. This 
gives very little trouble in making the order, and it is the 
greatest relief to the steel maker. It is his delight to get 
hold of such an order, for he knows that when it is filled he 
will hardly ever hear a complaint. 

Every steel maker worthy of the name knows exactly 
what temper to provide for any tool, or if it is a new case, 
one or two trials are enough to inform him, and as he always 
has all of his twenty odd tempers on hand, it is just as easy 
— and far more satisfactory to both parties — to have it made 
right as to have it made wrong. 

The Sheffield manufacturer, previously referred to, calls 



ON TEMPER OF STEEL. 29 

attention to this same experience, and very truthfully re- 
marks : 

" For many purposes, indeed, temper is of more impor- 
tance than quality. Nothing is more common than for steel 
to be rejected as bad in quality, because it has been used for 
a purpose for which the temper was unsuitable. We may 
divide consumers of steel into three classes : First, those 
who use their own judgment of what percentage of carbon 
they require, and instruct the manufacturer to send them 
steel of a specified temper; second, those who leave the se- 
lection of the temper to the judgment of the manufacturer, 
and instruct him to send them steel for a specified purpose ; 
and third, those who simply order steel of a specified size, 
leaving the manufacturer to guess for what purpose it is 
required. It cannot too often be reiterated of how much 
importance it is, when ordering steel, to state the purpose 
for which it is going to be used." 

And again : 

" You may depend upon it there is nothing so dear as 
cheap steel. It must be more economical to put five shil- 
lings' worth of labor upon steel that costs a shilling, to pro- 
duce a tool that lasts a day, than to put the same value of 
labor upon steel that costs only ninepence, to produce a tool 
that lasts only half a day. I am sure that the system 
adopted by some large consumers of buying tool steel by 
tender is one which in too many cases defeats the object for 
which it was instituted, and, by lessening the price, and con- 
sequently deteriorating the quality, causes the steel bill to be 
lessened at the cost of the labor bill, so that extravagance 
instead of economy is the result. In fact, it is an illustra- 
tion of the proverb about being penny wise and pound 
foolish." 



ON GAUGES. 




IN consequence of the absurdities and 
anomalies existing in our present system 
1 of gauges, we recommend the use of the 
i inch as a unit of measurement. 

There are in use at the present time 
three standard gauges, as follows : 



Nos. 



1 . 

2 . 

3- 

4- 

5 • 
6. 

7 ■ 

8 . 

9- 
io 
ii 

12 

i3 

i5 
16 

17 
18 

19 
20 

21 
22 



London. 

Decimals 

of one inch. 



•oS 3 
.072 
.065 
.05S 

•CM9 
.040 

•035 

•0315 
.0295 



Stubs'. 

Decimals 
of one inch. 



.300 

.2S4 

•259 
.2 3 S 
.220 
203 

.1S0 

•165 
.148 

•!34 
.120 

.109 

•095 
•0S3 

.072 

.065 

.058 

.049 

.042 

•035 
.032 

.028 



Brown 
& Sharpe's. 

Decimals 
of one inch. 



2S930 

25763 
22942 
20431 
1S194 
16202 
H42S 
12S49 

JI443 
101S9 
09074 
oScSi 
07196 
0640S 
05706 
05082 

04525 
04030 

03589 
03196 
02S46 

025347 



ON GAUGES. 



31 



Nos 



23 
24 

25 
26 

27 
28 

29 
SO 
31 
32 
33 
34 
35 
36 
37 
3S 

39 

40 



London. 

Decimals 
of one inch. 



.027 

.025 

.023 

.0205 

•O1S75 

.0165 

•0155 

•OI37S 
.OI225 

.OII25 

.OIO25 

.OO95 

.009 

.OO75 

.0065 

•00575 

.005 

•OO45 



Stubs 1 . 

Decimals 
of one inch. 



025 
022 
020 

01 8 
016 
014 

013 
012 
010 
009 
008 
007 

o°5 
004 



Brown 
& Sharpe's. 

Decimals 
of one inch. 



022571 

020I 

OI79 

OI594 

014195 

OI264I 

OII257 

OIOO25 

O1S928 

00795 

OO70S 

0063 

OO561 

OO5 

OO445 

OO3965 

OO3531 

OO3144 



In some cases the difference between two numbers falls 
as low as two thousandths of an inch, in others it is only one 
thousandth, etc. 

It may be possible to make one gauge to any of these 
standards which shall be so accurate as to defy the detection 
of an error, and with the same care it may be possible to 
make a thousand such gauges; but every mechanic, and every 
person accustomed to making accurate measurements of the 
best work, knows that it is simply impossible to obtain abso- 
lute accuracy in such pieces of work when produced in large 
quantities, and it is impossible commercially, on account of 
the cost. 

Every one knows of the wonderful accuracy of the Whit- 
worth gauges, and also their enormous price, which makes 
them almost unsalable. 

In regard to ordinary wire gauges, they are notoriously 



32 THE TREATMENT OF STEEL. 

inaccurate, because they cannot be made accurate and be at 
all salable. 

In a recent case a sample under discussion measured on 
one gauge tight twenty-three, and on the other light twenty- 
four, and our customer said it was neither by his gauge. 

A new gauge in our possession has its No. 23 so much 
larger than its No. 22 that the difference can be easily de- 
tected by the naked eye, yet No. 23 ought to be two to four 
thousandths smaller than No. 22. 

If we were to roll No. 23 by that gauge how "would our 
customer get what he wanted, unless his gauge accidentally 
contained the same blunder? 

Another trouble is with the wearing of the gauges, for 
which there is no remedy, and we imagine that no man ever 
throws away a gauge because it is worn out; on the contrary, 
it represents an outlay of several dollars, he is used to it, he 
measures everything by it, and he is mad when anything 
does not measure to suit it. A still more serious difficulty 
arises from a very common mode of ordering. We frequently 
have orders for such a gauge "light " or "tight," "full" or 
"scant," "heavy "or "easy," or such a number and one-half, 
for instance, 15^2. 

The latter is terribly confusing to a roller; he almost al- 
ways takes it to mean that it is to be thicker than the whole 
number, and is pretty certain to make it 14^-2 for 15^ if he 
is not warned beforehand. 

Then in regard to the terms "light," "easy," etc., we have, 
for instance, the differences between Nos. 27 and 28 in the 
three systems, as follows: 

.00225 .002 .001554 

or, two hundred and twenty-five hundred thousandths, two 
thousandths, and fifteen hundred and fifty-four millionths. 



ON GAUGES. 



33 



How is it possible for a roller to know just how many 
millionths of an inch another man, whom he never saw, 
means when he says No. 28 "full," or No. 27 "easy"? and 
how is he to guess how many thousandths of an inch the 
other man's gauge is wrong in its make, or how many hun- 
dredths it has worn in years of steady use? This is no fancy 
sketch ; the above are every-day difficulties in this age, when 
every man knows just what he wants and will have nothing 
else, and yet has no better way of telling his wants than to 
say I want such a gauge " tight," when probably his gauge 
differs from every other gauge that was ever made. 

There is a very easy 
and simple way out of this 
whole snarl, and that is to 
abandon fixed gauges and 
numbers altogether, and 
use the micrometer sheet 
metal gauges, which meas- 
ure thousandths of an inch 
very accurately, and even a quarter of a thousandth may be 
neatly measured. 

They are very simple, so that any boy of ordinary intelli- 
gence can be taught to use one in a very few minutes. They 
have very easy arrangements for readjustment when worn, 
and even when worn considerably they can be used accu- 
rately, without adjustment, by making allowance for the error 
in reading at the zero line. 

We find that mechanics like to work to them, and that 
there is very little trouble to get sheet rolling done to within 
a thousandth of an inch on fine sizes. 




COMPRESSED RODS. 




IN 1878 we concluded to undertake the 
manufacture of compressed drill rods, 
an article hitherto never successfully 
made in this country ; and we are now 
credited with the ability to furnish a 
product which, for quality and finish, 
cannot be surpassed. We are prepared 
to furnish the following sizes : 



COMPARE GAUGE WITH EXACT SIZES GIVEN IN THOUSANDTHS 

OF AN INCH. 





Sizes in 




Sizes in 




Sizes in 




Sizes in 


Nos. 


Decimals 


Nos. 


Decimals 


Nos. 


Decimals 


Nos. 


Decimals 




of 1 inch. 




of 1 inch. 




of 1 inch. 




of 1 inch. 


I 


0.228 


16 


O.177 


31 


O. I20 


46 


O.080 


2 


0.22I 


17 


O.I73 


3 2 


O. Il6 


47 


O.079 


3 


O.213 


18 


O. 170 


33 


O.I13 


48 


O.076 


4 


O.209 


l 9 


O. 166 


34 


O. Ill 


49 


O.073 


5 


O.206 


20 


O. l6l 


35 


O. no 


50 


O.070 


6 


O.204 


21 


0-I59 


36 


O. I06 


5 1 


O.067 


7 


0.20I 


22 


O.156 


37 


O. IO4 


52 


O.064 


8 


O.199 


23 


O.I54 


3S 


O. IOI 


53 


O.060 


9 


O. 196 


24 


O.152 


39 


0. IOO 


54 


O.054 


10 


O.194 


2 5 


O.15O 


4° 


0.098 


55 


O.052 


11 


O. 191 


26 


O. 148 


4 1 


0.096 


56 


O.O47 


12 


0.1SS 


27 


0-H5 


42 


0.094 


57 


O.O44 


13 


0.185 


28 


O. 141 


43 


0.089 


58 


O.O42 


14 


0. 182 


29 


O.136 


44 


0.086 


59 


O.O4I 


15 


0. 180 


30 


O. 129 


45 


. 082 


60 


O.O4O 



34 



en 

o 



1— 1 


M) 




c 


~o 


c 


o 


© 


C/5 


■o 


C/D 


(8 


o> 


X 


s_. 


t- 


Ql 





E 


■•J 

o 


o 


fc 


o 


CD 


■» 


£ 


■"■ 




~c^ 


o 


"o 




<D 




<"*> 


C3 


CO 


00 




0) 


-f— ' 


£ 

(0 

w 


CI 


<X> 


O 


© 


C/5 


£ 


<D 


** 


s— 


E 


O 





^ 


u. 


-o 




<D 




c~ 




c£ 




~o 




Q_ 






COMPRESSED RODS. 



31 



LETTER SIZES OF WIRE. 



A 


0.234 


H 


0.266 


O 


0.316 


U 


0.368 


B 


0.238 


I 


0.272 


P 


0.323 


V 


0.377 


C 


0.242 


J 


0.277 


Q 


0.332 


w 


0.386 


D 


0.246 


K 


0.2S1 


R 


o-339 


X 


0.397 


E 


0.250 


L 


0. 290 


S 


0.348 


Y 


0.404 


F 


0-257 


M 


0.295 


T 


o.358 


z 


°-4'3 


G 


0.261 


N 


0.302 











and in addition nearly all diameters from No. Z up to 7-16 
of an inch. 

We guarantee these rods to show results unsurpassable by 
any others, if hardened at the proper heat, by which we 
mean just that heat which will produce the peculiar condition 
known as "refined by hardening." In no other condition is 
hardened steel at its best. 

Advantages: no cracks ; less change in shape and size; 
great tenacity, combined with extreme hardness ; certainty 
insured of doing that which would be impossible with tools 
hardened at so high a heat as to require the temper to be 
drawn, to prevent breaking. 

In cases where extremely hard material is to be cut, tools 
may be used without drawing the temper. To determine the 
proper heat, break from the end of a bar a short piece, keep- 
ing the fracture clean. Harden the end of the bar from 
which the piece was broken at a low heat. If the hardened 
end requires less force to break it than before, and is as coarse 
or coarser, the heat was too high. If the heat was right, the 
hardened piece will be stronger, and the grain will be many 
times finer than before hardened. By following these simple 
instructions, remembering that the smaller the piece operated 
upon, the less heat is required to harden it, and the more it 
will be injured if the heat is too great; after a few experi- 



36 THE TREATMENT OF STEEL. 



ments, uniform results should be obtained, as the quality of 
the steel is strictly uniform. 

These rods are not made to gauges, which from lack of 
uniformity in size, aggravated by the natural wear in use, are 
a source of much trouble : but by actual measurement, in 
decimal parts of an inch, to correspond with the foregoing 
list. Customers adapting their work to these sizes may rest 
assured that orders for the same numbers will always bring 
them the same sizes, as nearly as it is possible for wire to be 
made. 

In conclusion, we reproduce a paper prepared by our Mr. 
Metcalf, and read before the Engineers' Society of Western 
Pennsylvania, Pittsburgh, Pa., January 20, 1880, entitled 
"Why does Steel Harden?" 



WHY DOES STEEL HARDEN? 




J HE inquiry has been pursued dili- 
gently by Prof. John W. Langley and 
ourselves for the past five years, and 
has been directed exclusively to the 
gathering of facts, so that as yet we 
have not even a theory to offer. The 
inquiry may be divided as follows : 
i. The physical structure of steel. 

2. The chemical composition. 

3. The variations of structure and physical properties 
due to — 

a. — Cooling from fusion. 

b. — Effect of work, either by rolling or hammering. 

c. — Effect of temperature, and of changes from one tem- 
perature to another, as shown by slow cooling or rapid 
cooling. 

4. A statement of the various theories of hardening. 

5. Some practical conclusions for workers of steel. 
1. The physical structure of steel. 

In this paper it is to be understood that reference is made 
only to cast steel. 

Steel is crystalline in structure. The size, color and form 
of the crystals, when steel is allowed to cool without hin- 
drance, from a state of fusion, are governed by its chemical 
constitution, and are mainly influenced by the quantity of 

carbon present. 

37 



^8 THE TREATMENT OF STEEL. 







2. The chemical composition of steel. 

Steel is mainly an alloy, compound or mixture of iron 
and carbon. 

Exactly which of these it may be, or whether it is a com- 
bination of two or of all three of these conditions, it is 
difficult to say. 

Other elements, as silicon, phosphorus, sulphur, manga- 
nese, and so on, are as yet present only by sufferance, and 
generally it is well known that steel is better without any of 
them. 

The range of carbon in commercial steel may be said to 
be from about .05 per cent to 1.75 or 2 per cent, but for 
some purposes of this inquiry we may look at several proper- 
ties of cast iron as being useful to throw light on the subject. 

3. The variations of structure and physical properties 
due to — 

a. — Cooling from fusion — as affected by chemical compo- 
sition, temperature, and rate of cooling. 

The structure of steel, and of cast iron, as shown in a 
fresh fracture of the ingot in one case, or the pig in the 
other, are remarkable as always indicating the quantity of 
carbon present, the temperature at which the metal was 
poured, and the rate of cooling. 

As the observation of these phenomena furnishes material 
for the study of a lifetime, and as they cannot be described 
properly without the objects themselves, only a few well 
known facts will be mentioned, for use in the latter part of 
this paper. Cast iron, when poured into iron moulds, hard- 
ens just as steel does when quenched in water; this is known 
as " chilling." 

A chill is of silvery white color, bright luster, and consists 



WHY DOES STEEL HARDEN? 39 

of elongated crystals generally normal lengthwise to the sur- 
face of the mould. 

If iron contains little or no silicon, it will chill very deep, 
or entirely through the mass in small castings. 

If much silicon be present it will not chill at all. 

If a hard chill, — for instance in a hammer die, — say two 
inches thick of chill, be brought to a red heat, removed from 
the fire at once and allowed to cool slowly, it will, when 
broken, be found to be softened, but it will retain the marked 
crystalline form of the chill. This is analogous to tempered 
steel. 

If the same chill be heated red, and kept red hot for sev- 
eral hours, and then cooled slowly, it will be found upon 
breaking to be an entirely amorphous gray cast iron ; every 
trace of the elongated crystals of the chill will have disap- 
peared. 

This is analogous to annealed steel. This experiment is a 
striking example of iron and combined carbon in the one 
case, and of iron and graphitic carbon in the other case, as 
these conditions are commonly understood. 

This observation is useful in understanding similar changes 
which occur in steel under the similar conditions of hardened, 
tempered and annealed steel. 

Steel when cast is almost invariably poured into iron 
moulds, and the study of fractured ingots is very necessary 
to the steel-maker; but as the ingots very rarely go into the 
hands of the consumer without previous manipulation, it is 
hardly necessary to consume time in discussing the charac- 
ters of the fractures, especially as it requires the actual pres- 
ence of the ingots to make the description at all intelligent. 

It is sufficient to say that we have here an unvarying rec- 
ord of the completeness or incompleteness of the fusion, of 



40 THE TREATMENT OF STEEL. 

the rate and temperature of the pouring, and of the chemical 
character of the steel, especially as it relates to carbon. 

b. — Effect of work, either by hammering or rolling. 

Steel, when heated and hammered or rolled from the 
ingot, has its specific gravity largely increased, its strength is 
greatly increased, and its grain is made very fine and uni- 
form ; this is called " hammer refining," to distinguish it from 
the refining due to hardening. 

An eminent Russian engineer has illustrated this hammer 
refining beautifully by comparing the hot steel to a certain 
solution of a salt. 

If the solution be allowed to precipitate slowly and undis- 
turbed, very large crystals will be formed, but if it be vio- 
lently shaken, the crystallization is hastened and very fine 
crystals are formed. 

So if steel be heated quite hot, but not so as to burn it, 
and be allowed to cool very slowly, it will form in very large, 
bright crystals and be very friable ; but if as soon as it is 
hot it be taken to a heavy hammer and be thoroughly ham- 
mered by rapid and powerful blows at first, and then by 
lighter blows until it is of the required shape, it will be 
found to be very fine in grain and very strong. 

Therefore, a high softening heat is consistent with good 
work in forging. 

c. — Effects of temperature, and of changes from one tem- 
perature to another, as shown by slow cooling or rapid 
cooling. 

The effect of heating steel which has been hammered or 
rolled is to increase the size of the crystals or grain, in pro- 
portion to the temperature, and to reduce the specific 
gravity. There is an apparent or real exception to this in- 



WHY DOES STEEL HARDEN? 41 



crease in size of grain in steel which has been hardened from 
the proper temperature to produce what is known as " re- 
ning. 

In this case the grain is much finer than in the bar, and 
in this condition any piece of hardened and tempered steel 
is at its best. 

As this refining temperature varies with every different 
quantity of carbon, no rule can be laid down for determining 
it; it must be found by actual trial. 

But there is no exception to the matter of specific grav- 
ity. The specific gravity of refined steel is less than that of 
the bar, although the grain is much finer. If steel be heated 
and cooled slowly it will be softened ; that is, annealed. 

If it be heated very hot, say to bright yellow, Or kept hot 
a long time, and then cooled slowly, it will still be annealed, 
but it will be harsh and gritty, will not cut well, and will 
neither refine well when hardened nor hold a good edge 
when tempered. The cause of this will be obvious if we re- 
member the experiment of the annealed chill mentioned in 
the earlier part of this paper. If steel be heated to different 
degrees, as red, bright red, orange, lemon or bright yellow 
color, and quenched, it will be found to be harder, more 
brittle, and coarser in the grain for each increasing degree of 
heat, after the "refining " heat has been passed. Below the 
"refining" heat there will be no useful degree of hardening, 
and the grain will be variable. 

If any piece of hardened steel be heated red hot, and 
cooled slowly, it will be softened, the grain of the steel will 
return to its original appearance in the bar, and its specific 
gravity will be restored to the specific gravity of the bar. 

This fact should put a quietus upon all quack nostrums 
for " restoring burnt steel." 



42 THE TREATMENT OF STEEL. 

If a piece of steel containing little carbon be alternately 
hardened and heated and re-hardened a number of times, it 
will vary in volume, but will not sustain regular increases of 
volume. 

If steel of moderately high carbon be repeatedly hardened 
it will continue to increase in volume until ruptured. This 
will be illustrated by table No. 5. 

Some years ago twelve ingots were selected by numbers, 
and analyzed to determine the accuracy of ocular inspec- 
tion, and were afterward experimented upon in following up 
the search for facts in regard to the cause of " hardening." 

The specific gravities of these ingots were determined, and 
the results were given by Prof. Langley in a paper read be- 
fore the American Association for the Advancement of Sci- 
ence, in 1876. Since then, bars rolled from these ingots 
have been experimented upon, and the specific gravities of 
the bars and of various hardened pieces and of re-softened 
pieces have been determined. 

These experiments will now be described. 

Table I gives the analyses and specific gravities of the 
ingots. 

Table II gives the specific gravities of six of the bars, 
and the specific gravities of the same bars heated to various 
temperatures and hardened. 

Table III gives the specific gravities of the six bars, and 
the six hottest pieces numbered 1 in Table II, after having 
been annealed from the condition given in Table II. 



WHY DOES STEEL HARDEN? 



43 



TABLE I. 



Ingot Numbers. 



2. 
3- 
4- 

5- 

6. 

7- 
8. 

9- 
io 

ii 

12 



c. 


Si. 


Ph. 


s. 


Fe. by 
Difference. 


.302 


.019 


.047 


.018 


99.614 


.490 


•034 


.005 


.016 


99-455 


•529 


•043 


.047 


.018 


99-3 6 3 


.649 


•039 


.030 


.012 


99.270 


.Soi 


.029 


•035 


.016 


99.119 


.841 


•039 


.024 


.010 


99.0S6 


.867 


•057 


.OI4 


.01 S 


99.044 


.871 


•053 


.024 


.012 


99.040 


•955 


•°59 


.070 


.016 


98.900 


1.005 


.088 


•034 


.012 


98.861 


1.058 


.120 


.064 


.006 


98-752 


1.079 


•039 


.044 


.004 


98.834 



Sp. Gr. 

Ingots. 



7-855 
7.836 

7.84I 
7.S29 
7.838 
7.824 
7.819 
7.S18 

7-313 
7.807 

7.S03 

7.805 



Table IV gives the specific gravities of four pieces, all 
from the same bar, after various treatment. 

Table V gives the results of repeated hardening of three 
pieces of steel containing different quantities of carbon. 
Consideration of the tables. 

Table I contains the analysis of twelve ingots, numbered 
in the left hand column from 1 to 12. 

The ingots were selected by the eye and numbered as in 
the table by Mr. Charles Parkin, with a view to varying 
quantities of carbon only. 

It will be seen that the carbon increases with the num- 
bers regularly, but not uniformly. 

Although a repetition of the analyses of Nos. 7 and 8 
confirm Prof. Langley in the correctness of his figures, it 
must be admitted that in this case Mr. Parkin was quite as 
lucky as skillful, for it is hard to believe in a really observa- 
ble variation of structure due to a difference of only 0.004 
carbon. 



44 



THE TREATMENT OF STEEL. 



In the columns for Si. Ph. and S. the entire absence of 
progressive quantities shows clearly that these elements had 
nothing to do in determining the characteristic fractures. 

The column of iron by difference happens to run with 
the carbon column, except in No. n, where the series is 
broken by the abnormal amount of Si. in that ingot. Theo- 
retically, of course, the specific gravities should run with the 
iron by difference, but they do not do so in ingots 3 and 5. 
These, however, are the only exceptions ; this may have 
been caused by incomplete or unusually hot melting, or by 
hot or cold pouring, or by slow or fast pouring. 

These exceptions do not vitiate the rule, and only show 
that no one set of experiments can be conclusive. 

TABLE II. 



3-- 
4- 
6.. 
8.. 
10. 





U 




1* 




v. 




u 










bio 


rt 


V 




£ *> 


n 


v r 


a 




a 




rt 


O, 




c 


. 


02 c 


W4 


Iffl 


oa . 


c a 
JJ03 






a . 


u 

O 


o| 


>- 


O^ 




Z* 


*£ 


66 


• - 


6 i 




5 I 


a 

CO 


0. 





co^ 


fcQ 


a, 

CO 


q£ 


a. 

CO 


P£ 


a. 

CO 

7.814 




a. 

CO 

7.818 


7.841 


7.844 


• 003 


7.831 


-.013 


7.826 


-.018 


7.823 


-.021 


-.030 


7.82a 


7.824 


-.005 


7.806 


-.018 


7 849 


.025 


7.830 


.006 


7 .8n 


-.013 


7-791 


7.824 


7.829 


.005 


7.812 


-.017 


7.808 


-.021 


7.780 


-.049 


7-7«4 


-°35 


7.789 


7.818 


7.825 


.007 


7.790 


-°35 


7-773 


-.042 


7-75 8 


-.067 


7 • 755 


-.070 


7-752 


7.807 


7.826 


.019 


7.812 


-.014 


7-7«Q 


-037 


7-755 


-.071 


7-749 


-.077 


7-744 


7.805 


7.825 


.020 


7. 811 


-.014 


7.79a 


-.027 


7.769 


-.056 


7-741 


-.084 


7.690 






026 

°33 
040 

073 
082 

'35 



6 


5 


4 


3 


2 


1 




Not 
heated. 


Low red 
heat. 


Red 

hot. 


High 
red. 


Yellow 
hot. 


Nearly white 
Scintillating. 



The twelve ingots under consideration were hammered 
to 1 % inch square bars at one end, and these bars were 
rolled to .625 diameter round bars. 

Six of these bars, Nos. 3, 4, 6, 8, 10, 12, were selected for 
specific gravity tests ; bar No. 2 was lost, or it would have 
been used instead of No. 3. 



WHY DOES STEEL HARDEN? 45 

Six nicks were made around each bar at one end at inter- 
vals of about half an inch. 

The six pieces were numbered from 1 at the end to 6. 

Each notched bar was then heated until piece No. 1 was 
scintillating or nearly white hot; No. 2 was yellow hot; 
No. 3, high red hot; No. 4, red hot; No. 5, barely showing 
any red, or very low red hot ; No. 6, black. 

This heating was done in each case as slowly and as care- 
fully as possible. The results show the inevitable irregulari- 
ties attending only one such experiment, yet there is enough 
of regularity to teach us a great deal. 

As soon as the heats were obtained the bars were quenched 
in water. 

The pieces, carefully numbered, both with the ingot num- 
bers and with the numbers giving their order on the bars, 
were then broken off and sent to Prof. Langley to have the 
specific gravities determined. In the table the left-hand 
column gives the ingot numbers. 

The other columns give the specific gravities of the 
ingots, the bars, No. 6 pieces, and of the other five hardened 
pieces in order, as numbered in the sketch and explained 
before. 

The differences are, first, the difference between the Sp. 
Gr. of the ingots and the bars; second, the difference be- 
tween the Sp. Gr. of the bar, or piece No. 6, and each piece 
successively. 

The differences of Sp. Gr. are given in preference to the 
actual differences in volume, because the differences in vol- 
ume run into the infinitesimals, and the mode adopted 
answers as well for purposes of comparison. 

On comparing the ingot and bar we see a decided increase 
in the Sp. Gr. of the bar in every case except one, that of 



46 THE TREATMENT OF STEEL. 

No. 4. We have not discovered the reason of this anomaly. 
The increase in the other cases is due to hot working; this 
will be shown by Table IV. 

It will be observed that the Sp. Gr. of the bars, except in 
No. 3, is nearly uniform. 

This seemed very strange at first, but it is capable of a 
very simple explanation. The hardness of steel and its re- 
sistance to change of form increase very rapidly with an 
increase of carbon, and as these bars were all reduced from 
3 in. square ingots to S-g in. round bars, it is obvious that it 
required much more work to reduce No. 12 than No. 4 or 
No. 6 ; therefore, as hot working increases Sp. Gr., the greater 
amount of work produced the greater increase in the Sp. Gr. 
of No. 12. 

If the Sp. Gr. of the right-hand column pieces No. 1 be 
compared to the Sp. Gr. of the ingots, it will be seen that 
the relation between the numbers is entirely restored by the 
high heat to which the No. 1 pieces were subjected. 

If the Sp. Gr. of pieces Nos. 5, 4, 3 be examined care- 
fully, sufficient irregularities in the difference columns will 
be observed to show that the heating was not accomplished 
in regular gradations in each case, and if it were desired to 
lay down an exact law of variation due to differences of tem- 
perature, it would be necessary to take the mean of a great 
many experiments. 

Nevertheless, several general laws are indicated in this 
table. 

1. The Sp. Gr. of the ingot varies directly with the quan- 
tity of iron present. 

2. The greater the quantity of carbon present, the greater 
is the amount of work necessary to produce change of form. 



WHY DOES STEEL HARDEN? 



47 



3. The greater the quantity of carbon present, the greater 
is the change in volume due to a change of temperature. 

As, for example, in No. 3 the change in Sp. Gr. from the 
ingot to the bar is only .003, and from the same bar to the 
piece No. 1 the change is .026. 

While in No. 12 the change in Sp. Gr. from the ingot to 
the bar is .020, or about seven times that in No. 3, and the 
change from the bar to the piece No. 1 is .135, or about five 
times the change in No. 3. 

This is perhaps the most important observation that can 
be made on this series of experiments, as it shows us why it 
is that high steel is so much more liable to crack and break 
in manipulation than low steel. 

We generally say one is brittle and the other is ductile; 
we now know that the rate of expansion per degree of tem- 
perature is much less in low steel than in high steel. There- 
fore, low steel is much less liable to injurious internal strains 
than high steel. 

TABLE III. 



Ingot 
Numbers. 


Sp. Gr. of bars. 
No. 5. 


Sp. Gr. of burned pieces. 
Annealed, No. i. 


Difference. 




7-844 
7.824 
7.829 

7-825 
7.826 

7-825 


7-857 
7.846 

7-835 
7.828 
7.824 

7.822 


+ .013 
+ .022 




6 


+ .006 


8 


+ 003 
— .002 


10 




—.003 



In order to settle the question of restoring " burned steel," 
so called, and also to determine the reverse action due to 
annealing, Prof. Langley took the six pieces No. 1 of Table 
II, and heated them all to a high yellow heat. He then 
allowed them to cool very slowly. 



4 8 



THE TREATMENT OF STEEL. 



This raised a heavy scale on the pieces, which was re- 
moved by touching them on an emery wheel. 

The specific gravities of these pieces were then taken, and 
the results are given in the table. 

The restoration to the Sp. Gr. of the bar is complete, as 
the differences are only such as might be due to the scale on 
the original bars and the removal of the scale from the 
annealed pieces. This will be shown further in Table IV. 



TABLE IV. 

DRILL ROD SAMPLES. 



Nos. 


i 
Sp. Gr. 


2 

Sp. Gr. 
Hardened. 


Sp. Gr. 

Scaled and 
not hardnd. 


Diff. 

3-2 

Effect of 

hardening. 


Diff. 

3-4 

Effect of 

scale off in 

1 and 2. 




7.S068 

7-794 
7.816 

7.787 


7.818 
7.812 
7.79O 
7-765 


7.829 

7.828 
7.817 

7-7SO 


— .Oil 

— .Ol6 

— .027 
—OI5 


+ .022 


2 


+ .034 
+ .OOI 






— .007 





It is well known that cold rolling does not increase the 
Sp. Gr. of iron or of steel. To ascertain the effect of cold 
hammering under the best conditions to increase Sp. Gr., 
namely, by hammering between semi-circular dies, an experi- 
ment was made, the results of which are recorded in Table IV. 

A round bar, of carbon about one per cent, was operated 
upon. 

The bar, as it came from the rolls, and unannealed, was 
0.682 inch in diameter; this is No. 1 in the table. 

A piece of the same bar, annealed and pickled, was 0.673 
inch in diameter; this is No. 2 in the table. 

The same bar twice hammered cold, after annealing, was 
reduced to 0.624 inch in diameter; this is No. 3 in the table. 



WHY DOES STEEL HARDEN? 49 



The same bar annealed, and hammered cold four times, 
was reduced to 0.564 inch in diameter; this is No. 4 in the 
table. 

Prof. Langley first took the Sp. Gr. of the four pieces as 
he received them, 1 and 2 having the roll scale upon them, 
and 3 and 4 being bright polished, all having been boiled in 
dilute potash and slowly cooled. The results are given in 
column No. 1. 

In this case No. 3 indicates an increase of Sp. Gr. due to 
the cold hammering. Prof. Langley then thinking that the 
results might have been affected by scale in the first two 
pieces, next removed the scale and boiled them all in weak 
potash, and upon removing them from the boiling liquid 
cooled them rapidly by plunging them quickly into cold 
water. 

Column No. 2 gives the results, and here we have the 
remarkable fact that sudden cooling from boiling tempera- 
ture causes a hardening effect, which is shown more particu- 
larly in Nos. 3 and 4, where there is a decided reduction of 
Sp. Gr. 

If subsequent trials prove this deduction to be correct, it 
is very important. Desiring to fortify himself as to this 
matter of hardening at such a temperature, Prof. Langley 
again boiled the pieces and allowed them to cool very slowly, 
thus annealing them. The results are given in column No. 3. 

Here is a progressive reduction of Sp. Gr., showing that 
cold hammering as well as cold rolling reduces Sp. Gr. The 
restoration of the Sp. Gr. of 3 and 4 to the results in column 
No. 1 shows that there was a hardening due to quenching 
from boiling temperature. The column of differences 3 and 

2 shows the effect of hardening. The column of differences 

3 and 1 shows the effect of removing the scale. This column 



5o 



THE TREATMENT OF STEEL. 



also accounts for the increase of Sp. Gr. shown in the "re- 
stored" or annealed pieces of No. i, Table I, recorded in 
Table III. The results recorded in Table IV have an im- 
portant bearing on the inquiry into the cause of hardening, 
which will be shown later. They are also important as show- 
ing the entirely mercurial or thermometric nature of steel. 
They also indicate a mode of accurate determination of the 
variable rate of change of volume in steels of different com- 
position. 

It will be remembered that there is such a variable rate 
of change clearly shown in Table I, and further evidence will 
be given in Table V. 

Now, by operating upon different samples by boiling, and 
sudden cooling in water of uniform temperature, we can get 
results which will range between certain uniform and known 
temperatures for each experiment. 

TABLE V. 

CHANGES IN VOLUME BY REPEATED HARDENING. 



No. of times 
hardened. 



I . 
2. 

3- 

4- 
5- 

6. 



Total change. 



Nos. 6 and 7, 

Table I. 

C = about .848 



Contraction of 
hole. 



.OOI72 
.OOI72 
.OO6SS 
.O06SS 
.0068S 
.OOOOO 

30044 crack'd 



.02752 



No. 4, Table I. 
C =.649. 



Expansion. 


Contrac- 
tion. 


.00172 
not cracked 


.OO257 
.OO086 
.OO482 

.OO172 
.OOOOO 




.OO771 



No. 3, Table I. 
C =.520. 



! Con> 
Expansion. ltraction . 



.OOI72 
.OO0S6 
.OO0S6 
not cracked 



.00000 



ckdoS6 
.00172 
.00000 



.000S6 



.00000 



Hole was originally .75 diameter. 



WHY DOES STEEL HARDEN? 5 1 



This is an experiment to find by measurement the effect 
of repeated hardening upon three pieces of steel containing 
different amounts of carbon. 

A hole about .75 inch in diameter was drilled in the mid- 
dle of each piece. The measurements were taken by means 
of a tapered plug, the difference in the distance to which it 
entered in each case, after the first and subsequent harden- 
ing, was measured by micrometer. The left-hand columns 
give the numbers of the successive hardenings. The other 
columns show the changes in the diameter of the hole. The 
first piece, of carbon .848, showed contraction of the hole 
every time it was hardened except the sixth, and the piece 
cracked at the seventh hardening. The operator supposes 
the sixth hardening was accidentally omitted. 

The second piece, of carbon .649, showed contraction 
three times, then no change. Then an expansion of the hole 
followed by a contraction, and the seventh time there was no 
change. This piece did not crack. 

The third piece, of carbon .529, showed two contractions, 
then no change, followed by three expansions, and seventh a 
contraction. This piece did not crack. 

The total changes are quite marked : 

Showing for carbon 84S = .02752 inch. 

" " " 649 = .0077 1 " 

" " " 529 = .00000 

This shows in another way that steel of high carbon 
changes more in volume per degree of temperature than 
steel of low carbon. 

The high steel cracked, the low did not. All the pieces 
were of the same quality. 

The experiment recorded in table No. V forms no part of 
the investigation by Prof. Langley and ourselves. It was 



52 THE TREATMENT OF STEEL. 

made rather crudely for a practical purpose, and the results 
obtained in practice confirm the figures in the table. 
This ends our record of facts and brings us to — 

4. A statement of some of the theories which have been 
given as the cause of hardening. 

Perhaps the oldest, one of the most plausible, and possibly 
the true reason, is that unhardened steel contains carbon in 
graphitic and uncombined form, and hardened steel has its 
carbon all combined. 

For proof it is stated that when unhardened steel is dis- 
solved, the insoluble residue contains flocculent graphitic 
carbon ; and when hardened steel is dissolved it leaves no 
residue of carbon ; therefore, the carbon has been combined 
in the hardening. To answer the objection to this, that it is 
impossible for iron and carbon to combine in all proportions, 
one writer states that there is formed a definite carbide Fe. 
C 4 . 

That this carbide is excessively hard, and that it acts as a 
cement or glue, and therefore the high carbon steel becomes 
so much harder than the low carbon steel. 

This will be conclusive after the carbide has been sepa- 
rated and thoroughly examined. Meantime, the hardening 
from boiling temperature is a little puzzling. 

Another writer states that solution of the carbon takes 
place when the steel is heated, and that a great compression 
caused by the sudden contraction in cooling is the cause of 
hardness. 

If this be so, and our experiments are correct, then carbon 
dissolves in steel at the temperature of boiling water. 

One writer hastens to inform us that steel hardens because 
part of the carbon is burnt out in heating, and the rest of the 
mass is compressed by the sudden cooling. It might afford 



WHY DOES STEEL HARDEN? 53 

amusement to demolish this theory, if it would not be a waste 
of time. 

A steel-maker of twenty years' practice says hardening is 
caused by the carbon assuming the diamond form, in very 
minute crystals. 

He gives, as a proof, that the hot steel decomposes water, 
or the cooling mixture, which always contains hydrogen. 

The hydrogen combines with the carbon to form diamonds, 
and this is proved by the fact that the diamond and hard- 
ened steel both refract light. 

In case water is the cooling medium, the hydrogen pene- 
trates the steel to form diamonds, while the freed oxygen, 
conveniently inert, stays on the outside to form a thin film of 
oxide. 

As it is well known that mercury is one of the very best 
cooling liquids, giving extreme hardness to steel, it is neces- 
sary to this theory to show that mercury contains hydrogen. 

Again, if steel really hardens upon being quenched from 
boiling temperature, then water must be decomposed by that 
temperature. 

This diamond theory is very attractive, and has received 
much consideration in our minds, but we are not prepared to 
consider it proven. 

Another writer states that hardening is due to the sudden 
arresting of the molecular motion that exists in the heated 
steel, thus causing great tension and resulting hardness. He 
offers, as proof, that hardened steel is weaker and more brittle 
than unhardened steel, and cites as a very happy illustration 
the case of hardened glass which is known to be in a high 
state of tension. This theory tallies with all the facts better 
than any we have seen. 

First, it covers all conditions, from the boiling tempera- 



54 THE TREATMENT OF STEEL. 

ture up to the high yellow heat which causes intense hardness 
and the brittleness of glass. 

Again, it is certain that the higher the heat the greater the 
molecular motion. Also it is certain that from the highest 
heat we get the greatest hardness, and the greatest brittle- 
ness. 

Finally, the restoration of grain, and of Sp. Gr. by anneal- 
ing, agree well with the idea of tension in one case, and the 
relief from tension in the other. 

It is possible, even if this tension theory be accepted as 
correct, that there may be, in connection with it, a change to 
diamond form, or from graphitic to combined carbon, and 
the formation of a definite carbide. Some one of these 
changes, taking place at a given temperature, may be just 
what is needed to expla : that very remarkable phenomenon 
known as "refining." 

In mentioning a few practical considerations to be drawn 
from what has been said, it is hardly necessary to address the 
unfortunate smith and temperer; they, poor fellows, have 
heard so much of uniform heating and low heating, that they 
may well feel heart-sick, and determined to do as they please 
anyhow. 

Let them do as they will, they will never be allowed to 
forget that same old cry — " too much heat" — " irregular 
heat" — and so on. 

Let that cry continue; it has its uses; and let us look at 
the engineer's side. 

As steel advances with irresistible steps into the field of 
construction, the engineer naturally asks — What am I to do 
with it ? 

Can it be worked safely ? 

Is it reliable ? 



WHY DOES STEEL HARDEN? 55 

Shall I use high steel or low? 
How is it to be worked ? 

Is it safe to use the apparent advantages of great strength 
to be had in high steel? 

Is it necessary to anneal finished work ? etc. etc. 

We think it has been clearly shown — 

1. That a good soft heat is safe to use if steel be immedi- 
ately and thoroughly worked. 

It is a fact that good steel will endure more pounding than 
any iron. 

2. If steel be left long in the fire it will lose its steely 
nature and grain, and partake of the nature of cast iron. 

Steel should never be kept hot any longer than is neces- 
sary to the work to be done. 

3. Steel is entirely mercurial under the action of heat, 
and a careful study of the tables will show that there must of 
necessity be an injurious internal strain created whenever 
two or more parts of the same piece are subjected to different 
temperatures. 

4. It follows that when steel has been subjected to heat 
not absolutely uniform over the whole mass, careful annealing 
should be resorted to. 

5. As the change of volume due to a degree of heat in- 
creases directly and rapidly with the quantity of carbon 
present, therefore high steel is more liable to dangerous in- 
ternal strains than low steel, and great care should be exer- 
cised in the use of high steel. 

6. Hot steel should always be put in a perfectly dry place 
of even temperature while cooling. A wet place in the floor 
might be sufficient to cause serious injury. 

7. Never let any one fool you with the statement that his 
steel possesses a peculiar property which enables it to be 



56 THE TREATMENT OF STEEL. 

"restored" after being "burned;" no more should you waste 
any money on nostrums for restoring burned steel. 

We have shown how to restore " overheated" steel. 

For " burned" steel, which is oxydized steel, there is only 
one way of restoration, and that is through the knobbling fire 
or the blast furnace. 

" Overheating" and " restoring" should only be tried for 
purposes of experiment. The process is one of disintegra- 
tion, and is always injurious. 

8. Be careful not to overdo the annealing process ; if 

carried too far it does great harm ; and it is one of the com- 
monest modes of destruction which the steel-maker meets in 
his daily troubles. 

It is hard to induce the average worker in steel to believe 
that very little annealing is necessary, and that a very little is 
really more efficacious than a great deal. 

Finally, it is obvious that as steel is governed by certain 
and invariable laws in all of the changes mentioned, which 
laws are not yet as clearly defined as they should be, nor as 
they will be ; nevertheless, the fact that there are such laws 
should give us confidence in the use of the material, because 
we may be sure of reaching reliable results by the proper ob- 
servance of the laws, therefore there is no good reason why en- 
gineers should be afraid to use steel if they manipulate it in- 
telligently. Now, if we have wandered over a wide range in 
answer to the simple question — " Why does steel harden ?" — 
it was necessary to have looked at many facts before we could 
have an intelligent opinion of many theories ; and if any are 
in doubt as to what is the correct answer to this momentous 
question, we can only say that we are all in the same boat, for 
if you do not know, neither do we. 




Overheated steel tells its own story. 

A high heat opens the grain of steel and prevents 
refining. 

Cast steel properly hardened is invariably refined thereby. 

The temper of steel is regulated by percentage of carbon. 

The iron used in making steel determines its quality. 

Consumers of steel should be guided by makers' advices. 

Sulphur is an enemy to steel. 

Good fuel is essential to best results in working steel. 

Charcoal, from sound wood, is the king of fuels. 

Avoid exposing hot steel to draughts of air. 

Pure water is a good hardening medium. 

Cherry red is a safe heat for steel. 

Nick cold steel with sharp chisels. 

A good softening heat, for forging, can be safely used if 
proper precautions are observed. 



57 



58 THE TREATMENT OK STEEL. 

The lead screws of lathes are often responsible for inac- 
curacies in the threads of taps. 

Large pieces may often be protected in heating by being 
covered with a coating of dry clay. 

No annealing is better than over-annealing. 

Be sparing of the blast. 

Time and care are necessary in the treatment of steel. 

Burnt steel is disintegrated steel. 

Properly constructed furnaces will pay for themselves in 
the value of tools which will be saved by their use. 

'"Soaking," or long continued heats, even if low, are in- 
jurious to steel. 

It requires a high order of talent to treat high grade steel 
successfully. 

In heating for hardening, great care should be taken with 
irregular shapes that no part of the piece be too hot. 

Steel which has been annealed at a high heat will not 
harden on the surface. 

A low red heat will anneal steel thoroughly. 

Do not try to harden steel that has been annealed, before 
turning off the surface. 

He is a good steel worker who never spoilt a piece of 
steel. 

Do not be deceived by nostrums for restoring burnt steel. 

The peculiarities and proper treatment of steel are stud- 
ies for a lifetime. 



SPARKS. 59 



Benjamin Huntsman is said to have invented the cast 
steel process in 1770. 

Crucible cast steel is recognized the world over as the 
best steel. 

Low priced steel may be very dear steel. 

Steel is mercurial and delicately responsive to heat; its 
records appear in its own structure. 

The last age : the age of steel. 

Dirty, slack fires put dirty sulphurous oxides on steel. 

The hardening heat varies with each temper of steel, and 
the only safe course is to harden at the lowest heat that, on 
trial, is found to give the required hardness. 

Hardening cracks are more often the result of uneven 
heating than of any defect in steel. 



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64 CRESCENT STEEL WORKS. 



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